The issue seems regarding aborting threads from what you indicate. I would try to just X out the 3D preview, and unfortunately use a quick render node to do small renders, or use a full render with crops to check your work. Not really the best solution.
I do wonder if this is just related to older hardware? Terragen liked to crash when it was aborting threads a lot when I used a compute stick, and it did the same thing when I emulated it on my LG G8, and had to pause/close preview to get the software to function. (Come to think of it, it was doing this under Windows 10 emulated on my server; which has full virtualization support to setup multiple OS's)
On Windows, UAC Support for legacy hardware/drivers shows disabled for Terragen (though can be enabled manually) so by default it may not be using anything it may need to on older hardware.
I posted this in the wrong thread....
